High temperature - high strength alloy glass fiber feeder

ABSTRACT

A high temperature-high strength alloy comprising platinum, rhodium and one or more metals consisting of molybdenum, tungsten, iridium, and rhenium is fabricated into apparatus adapted to receive and controllably emit molten material for attenuation into glass fibers.

United States Patent 11 1 Hansen et al.

HIGH TEMPERATURE HIGH STRENGTH ALLOY GLASS FIBER FEEDER Inventors: James H. Hansen; Ralph W. Getz, both of Newark, Ohio Assignee: Owens-Corning Fiberglas Corporation, Toledo, Ohio Notice: The portion of the term of this patent subsequent to Nov. 23, 1988, has been disclaimed.

Filed: Oct. 26, 1971 Appl. No.1 192,293

Related US. Application Data Continuation-impart of Ser. No. 884,689, Dec. 12, 1969, Pat. No. 3,622,289.

US. Cl 65/1, 65/374, 75/172 Int. Cl C03!) 37/02 Field of Search 75/172, 134 V; 65/1,

Primary ExaminerRobert L. Lindsay, Jr. Attorney-Robert E. Witt et al.

[57] ABSTRACT A high temperature-high strength alloy comprising platinum, rhodium and one or more metals consisting of molybdenum, tungsten, iridium, and rhenium is fabricated into apparatus adapted to receive and controllably emit molten material for attenuation into glass fibers.

1 Claim, No Drawings HIGH TEMPERATURE HIGH STRENGTH ALLOY GLASS FIBER FEEDER This is a Continuation-in-Part of our co-pending application, Ser. No. 884,689, filed on Dec. 12, 1969 now U.S. Pat. No. 3,622,289 granted Nov. 23, 1971.

BACKGROUND OF THE INVENTION This invention relates to platinum-rhodium alloys and more specifically to a platinum-rhodium alloy having a third metal addition wherein its high temperaturehigh strength properties are greatly increased. A high rhodium alloy is very desirable because of its high melting properties thereby being capable of exposure to high operating temperatures during service operations.

High rhodium content alloys in the past have been demonstrated to be capable of being produced without difficulty by a normal vacuum melting process. Platinum-rhodium alloys comprising from 20-40 percent rhodium are capable of being fabricated by a process of hot working followed by normal cold working. For example, in the case of sheet material, hot rolling is followed by cold rolling. Rhodium contents of more than 40 percent have been fabricated but they require more sophistication, e.g., powder techniques.

However, by increasing the rhodium content of these alloys their affinity for oxygen also increases, i.e. the oxygen solubility of the alloy increases thereby reducing the ductility of the alloy. Extreme care must be taken when using current production welding techniques (tungsten arc-inert gas shield) to prevent brittle welds. The chance of embrittlement due to oxygen absorption by these alloys is greatest during welding when the alloy is in the molten state. I

During service operation at elevated temperatures, the ductility of a high rhodium alloy is reduced by increased oxygen solubility thereby creating a potential for premature failure of the alloy due to stress cracking. Weld failures have been noted on fabricated parts of a high rhodium alloy when exposed to high temperature.

To improve the high temperature ductility of a high rhodium content alloy and also assure weld integrity, the following high rhodium alloy system has been developed; platinum 14 to 79 percent, rhodium 20 to 85 percent and a third metal addition of from 0.01 to 1.0 percent, wherein good homogenization of the third metal addition is required.

The third metal additions are selected from the refractory or platinum group metals, such as for example, iridium, tungsten, rhenium and molybdenum and combinations thereof. Originally selected for use as solid solution strengtheners to yield a stronger alloy, there metals have been found to increase the high temperature ductility of high rhodium content alloys.

SUMMARY This high temperature-high strength alloy finds immediate use in the glass fiber industry in bushings and other standard high-temperature applications. The development of such an alloy has been prompted by the increased emphasis on higher melting glasses wherein high strength requirements for bushings are necessitated because of the higher operating temperatures, characteristics of these glasses.

Among the problems encountered when a bushing is in service are the volatilization losses of the alloy from the bushing and creep deformation of the bushing structure which decreases the efficiency and life of the bushing and which lends to lower quality glass fibers.

The advantage of using an alloy of the inventive concept includes a reduction in the precious-metal volatilization losses from the bushing during service and improved strength characteristics of the alloy to reduce high temperature creep rates.

Molybdenum is the preferred third metal addition in the platinum-high rhodium content alloys of this invention because of their intended use in high-temperature resistant glass handling apparatus, although the other named third metal additions function in the same manner. Molybdenum is not known in the art to improve the ductility of the platinum-rhodium alloy, so that the use herein of small percentages of molybdenum to improve the ductility of a platinum-rhodium alloy is totally unexpected and unobvious. Very small additions of molybdenum to a platinum-rhodium alloy make it possible to use rhodium in proportions as high as 20 to 85 percent whereas in prior platinum-rhodium alloys, without molybdenum, the maximum practical rhodium content was limited to approximately 20 to 40 percent.

The percentage of the third metal addition that is added to the platinum-rhodium alloy is based upon the rhodium content, i.e. as the latter is increased so is the former. However, the amount of the third metal addition in the alloy should not exceed 1.0 percent by weight because of the potential of undesirable internal void formations developing during service applications which embrittles the alloy.

Some of the general characteristics of the alloy of this invention include improved tensile properties, slightly reduced oxidation losses of precious metal due to preferential oxidation of the third metal addition, improved high temperature ductility, improved creep rupture life, and improved weld integrity.

The ranges of proportions of the metals making up the alloys of this invention, expressed in weight percent, are:

platinum l4 79 rhodium 20 85 third metal addition 0.01 1.0

The preferred ranges expressed in weight percent are:

platinum 29 59 rhodium 40 third metal addition 0.05 0.75

The preferred composition of the inventive alloy, expressed in weight percent comprises:

platinum 40.0

rhodium 59.5

third metal addition 0.5

Molybdenum is the preferred third metal addition in the above compositions although the other named third metals and combinations thereof function in the same manner.

Examples .of the alloys of this invention, expressed in weight percent, include the following:

EXAMPLE I platinum 14.0 rhodium 85.0

molybdenum 1.0

EXAMPLE II platinum 79.00 rhodium 20.99

molybdenum 0.01

platinum 79.00 rhodium 20.99

iridium 0.01

EXAMPLE VII platinum 14.0 rhodium 85.0

rhenium 1.0

EXAMPLE VIII platinum 79.00 rhodium 20.99

rhenium 0.01

EXAMPLE IX platinum 59.00 rhodium 40.25

molybdenum 0.75

EXAMPLE X platinum 29.95 rhodium 70.00

molybdenum 0.05

EXAMPLE XI platinum 59.00 rhodium 40.25

tungsten 0.75

EXAMPLE XII platinum 29.95 rhodium 70.00

tungsten 0.05

EXAMPLE XIII platinum 59.00 rhodium 40.25

iridium 0.75

EXAMPLE XIV platinum 29.95 rhodium 70.00

iridium 0.05

EXAMPLE XV platinum 59.00 rhodium 40.25

rhenium 0.75

EXAMPLE XVI platinum 29.95 rhodium 70.00

rhenium 0.05

EXAMPLE XVII platinum 40.00 rhodium 59.5

tungsten 0.5

EXAMPLE XVIII platinum 40.0 rhodium 59.5

iridium 0.5

EXAMPLE XIX platinum 40.0

rhodium 59.5

rhenium 0.5

Examples of alloys of this invention which employ at least two of the third metal additions, expressed in weight percent, include the following:

EXAMPLE XX platinum 40.0 rhodium 59.0

molybdenum 0.5 tungsten 0.5

EXAMPLE XXI platinum 74.0 rhodium 25.0

molybdenum 0.5 tungsten 0.5

EXAMPLE XXII platinum 14.0 rhodium 85.0

molybdenum 0.9 rhenium 0.1

EXAMPLE XXIII platinum 59.0 rhodium 40.0

tungsten 0.3 iridium 0.7

EXAMPLE XXIV platinum 29.00 rhodium 70.00

tungsten 0.01 rhenium 0.99

EXAMPLE XXV platinum 40.00 rhodium 59.90

iridium 0.05

rhenium 0.05

EXAMPLE XXVI platinum 14.0 rhodium 85.0

molybdenum 0.5 tungsten 0.3 iridium 0.2

EXAMPLE XXVIl Platinum 30.0

Rhodium 69.5

Molybdenum 0.3 Tungsten 0.1 Rhenium 0.1

EXAMPLE XXVllI platinum 59.0 rhodium 40.0

tungsten 0.4 iridium 0.3

rhenium 0.3

EXAMPLE XXIX platinum 78.5 rhodium 20.8

iridium 0.1

rhenium 0.1

molybdenum 0.5

EXAMPLE XXX platinum 49.5

rhodium 49.5

molybdenum 0.5

tungsten 0.3

iridium 0.1

rhenium 0.]

Alloys containing platinum and a high proportion of rhodium typically exhibit very brittle characteristics unless their purity is very high and their gas content very low. Even the highest purity alloys, however, exhibit some brittleness especially after exposure to operating temperatures of l,800 F. to 2,750 F. Due to lattice changes with increasing rhodium. content, highrhodium alloys have a great affinity for gas, particularly oxygen. The addition of a third element, which forms a volatile oxide morereadily than platinum or rhodium tends to minimize the effects of impurities or dissolved gas on high rhodium content alloys. The effect of the third metal: addition on high content rhodium alloys may be theorized by one of the following phenomena: l the third metal element ties up and carries away oxygen thereby preventing formation of a thin film of oxide on grain. boundaries or (2) the third metal element ties up and carries away oxygen. much faster than the diffusion. of oxygen in the lattice network, thus preventing embrittlement or (3) the third metal element tends to further refine and degas the alloy during melting which results in improved properties, or (4) the thirdrmetal additions actsas an absorbing media for absorbed and dissolved oxygen in the alloy. It is theorized that the third metal addition is converted to a volatile oxide which inhibits oxygen absorbtion into the alloy. Thus the ductility of the alloy is maintained and the high rhodium alloy may be welded and used in high temperature service applications.

It is. therefore. an object of this invention to provide a platinum-high rhodium content alloy capable of being fabricated intodesired articles and capable of withstanding high' operating temperatures.

It is another objecttoprovide an alloy which is highly resistant to attack by molten glass and air, which has good creep (Creep. is. defined as deformation or elongation asa function of time ata uniform stress, usually athigh temperatures.) resistance, good creep-rupture life (Creep-rupture life is defined as the time until fracture at a given temperature and stress.), and which has high load carrying ability at elevatedtemperatures.

These and other objects will be readily apparent from the following detailed description which it intended only to illustrate and disclose the invention.

In a platinum-high rhodium content all oy, it is desirable to have a minimum creep rate, good creep-rupture life and high strength at high operating temperatures.

Alloys comprising a very high rhodium content (at least 20 percent) find application where service temperatures are very high (2,700 2,800F.)'or in high stress applications at moderate temperatures (220 2,600F.) to prevent excessive deformation thereof.

It is known that rhodium is a good hardener for a platinum containing alloy, i.e. it is a good solid solution strengthener and forms a continuous solid solution. Rhodiums oxidation resistance approximates that of platinum and is therefore the basis for selecting a platinum-rhodium system.

The third metal addition to the platinum-rhodium system adds stability to the system in that it extends the operating life of articles fabricated therefrom. The third metal addition forms an oxide more readily than platinum or rhodium and it volatilizes during welding operations whereby maintaining the ductility of the alloy. Without the third metal addition, the alloy would readily absorb oxygen and become brittle and thereby be impossible to fabricate and would have a shorter operating life.

Alloys comprising up to about 40 percent rhodium are commercially available but in order to increase alloy strength, the rhodium content must be increased. However, by increasing the rhodium content, the ductility of the alloy is adversely affected because of the oxygen absorption, hence the third metal addition is employed in the inventive concept to remedy the situation.

The criteria for the third metal addition(s) include (1) a capability of forming a volatile oxide above 1,800F. that volatilizes faster than platinum or rhodium, (2) a modulus higher than that of platinum or rhodium, (3) a suitable lattice structure (4) a high va- 7 lence state (7,8,9,), i.e. its free electrons are available for bonding purposes, to increase the alloys resistance to creep, and (5) a high melting point to withstand high service temperatures.

A desired article or apparatus is usually made from our platinum-rhodium alloy by forging and rolling it into sheet form, followed by fabrication and welding. However, the alloy of thisinvention is capable of being cast into shapes i.e. slinger cups, spinnerettes, etc.

A double vacuum melting process is preferred when making articles for use in high temperature applications to help insure a homogeneous mix and uniform properties throughout the alloy, and especially to help distribute losses of the third metal addition by volatilization.

When a bushing structure is fabricated for use at high service temperatures, it is sometimes desirable to make a composite structure comprising different alloys having the same constituents but different proportions. For example, the body, tip sections, and tips of a bushing structure may be fabricated from platinum-high rhodium content alloys whose compositions vary in order to meet specific operating temperatures. More specifically a lower content of rhodium (20-25 percent) in a platinum-rhodium-X ternary system may be used in a bushing body to help maintain proper bushing current distribution and to maintain ductility whereas a higher content of rhodium (up to 60 percent) in a platinumrhodium-X ternary system may be used in the tip section to reduce the creep deformation of the composite structure.

Electrical resistivity plays an important role in the selection of alloys for fabrication into bushings and other apparatus where electrical current is passed therethrough. As the rhodium content is altered in a platimum-rhodium system to obtain specific properties, the resistivity of the latter is altered. In order for these alloys having varying rhodium contents to be fabricated into composite bushings, varying amounts of the third metal are added in order to obtain a certain resistivity. That is, the composite structure requires the resistivities thereof to approximately be of the same magnitude. Therefore the resistivity of these alloys have been made to be a function of the amount of the third metal therein. The importance of the resistivities being of the same magnitude is because temperature differentials would arise as the resistivity varied, thereby decreasing 'the efficiency of the fabricated article, such as a bush- It has been observed that the addition of small amounts of a third metal to a platinum-rhodium alloy increases the contact angle of the alloy. This characteristic is critical in the manufacture of glass fibers to prevent a condition known as flooding from occurring. Contact angle is defined as 2 tan "h/X wherein h is the height of a molten bubble of glass on a particular substrate and x is the radius of the base of the bubble.

Flooding is defined as the covering or wetting of a substrate, such as the tip plate or sidewall of a feeder, housing hollow projections or tips, with molten glass which disrupts the formation of glass fibers. As the contact angle increases the tendency toward flooding decreases, thereby leading to a more efficient operation.

Composite bushing structures were fabricated from the platinum-rhodium-x ternary alloy systems of this invention, wherein the compositions for the sidewalls, tip plate, and tips were as follows, expressed in weight percents:

Platinum Rhodium Third Metal Addition Sidewalls 15 25 trace Tip plate 60 40 4O 60 up to 1.0 Tips 70 8O 20 30 trace The amount of the third metal added to each alloy was based upon the rhodium content of the alloys so that the composite structure possessed substantially uniform electrical resistivity. Molybdenum is the preferred third metal addition in the above composition ranges for alloys employed in a composite bushing structure. However, the other named third metal additions and combinations thereof function in the same manner.

We claim:

1. A glass feeder, comprising sidewalls, and a plurality of hollow projections extending outwardly from a particular sidewall, adapted for containing and controllably emitting a plurality of streams of molten glass for formation into glass filaments, fabricated from an alloy consisting essentially of, by weight percent, platinum 14-79, rhodium 20-85 and molybdenum 0.0ll.0. 

